1. Technical Field
The present invention pertains to wireless communication systems. In particular, the present invention pertains to controlling transmission of network node routing and/or topology information throughout the network to reduce network overhead traffic.
2. Discussion of Related Art
In a mobile ad-hoc network (MANET), the locations and start-up sequence of radios or nodes are random. During the start-up phase, individual nodes communicate using network formation packets, adjacency or neighbor management packets and routing/topology information packets (Link State Advertisement (LSA)) to form and maintain a network. Since channel bandwidth is very limited in a wireless environment, overhead traffic loads used for forming a network must be maintained at minimum levels. However, these levels should not excessively penalize the performance of the network. Even in a stationary scenario, the network topology changes as more nodes are enabled and added to the network during network initialization. In a mobile scenario, the network topology similarly changes when nodes move within and out of range with each other.
In order to maintain a node routing and/or topology database current and synchronized with the entire network, LSA packets are triggered in response to important changes in network topology. The triggered LSA packets are flooded throughout the entire network. Since there are numerous changes during the initial network start-up, several new LSAs are generated. If a network is stable, certain entries within a node routing database are not likely to change much once these have been determined. However, other entries continue to change as node groups are being formed within the network (with each node group including a head node). The new LSAs triggered by changes in communication links are needed for radios or nodes to establish routes for message delivery. This information enables a radio or node to find shorter routes. Thus, the flooding of these LSAs is worthwhile since shorter routes improve the message delivery time and provide fewer transmissions and faster data channel availability. This flooding further reduces collisions and improves the message completion rate.
New LSAs triggered by changes in other parameters similarly add to the overhead traffic load. However, the benefits of flooding these LSAs are not as worthwhile. For example, flooding an LSA in response to a change in a node group size provides minimal benefits, especially for a network including a single node group since the node group is aware of the group size.
With respect to a network including plural node groups, the node group size is generally used in group merge operations. However, group member nodes do not have direct usage for this information in these types of operations, while the group head nodes already have current information on their own group size. Thus, the additional overhead traffic produced from LSAs triggered by changes in these types of parameters is significant and an extra burden on the network since the flooding is done by every radio or node in the group, and the load may grow rapidly in accordance with network conditions.